The present invention relates to annunciators for indicating the presence of a vehicle which is desirous of being serviced.
The promulgation of weight limit laws for super highways in the past has led to the establishment of numerous weigh stations or truck scales in order to ascertain compliance with the individual state laws regarding maximum load limits. Heavy duty transport trucks are required to pull off of the road into the weighing station whereupon the truck drives onto a weighing platform. Each axle of the truck is driven over the weighing platform with the result that the weight of the truck is checked against the maximum permissable amount by the operator. In order to signal to an operator that a truck is present and is awaiting the required weighing, it has become increasingly common to utilize a signaling device whereby passage of the truck over the device rings a bell signaling the operator to begin the weighing process.
One prior art example of such a weighing device is the apparatus commonly used in gasoline stations to indicate the passage of a car to a gas station attendant who is otherwise occupied. The system generally consists of a hose having one end sealed and the other end connected to a pressure switch. Passage of an automobile or a truck over the hose compresses the hose changing the internal pressure and activating the pressure switch. Operation of the pressure switch would cause a bell or other sensory device to operate and signal the attendant. Unfortunately, these systems have numerous disadvantages. When an extremely heavy truck passes over the hose the hose tends to shift position and generally fails to stay in its proper place. During cold weather operations, the pressure switch has a tendency to freeze up and fail to operate. During wet weather, the pressure switch would short-circuit causing the signaling device to operate and provide an erroneous indication to the attendant. Furthermore, any device that passed over the indicating system would operate the signaling device even if the vehicle was not waiting to be weighed. Furthermore, if the vehicle stopped on the hose, the bell or other sensory device would operate continuously much to the distraction and annoyance of the attendant.